I wanted to write a thread about this here so others could find it, I researched a lot and found this method in one or two random places on the internet, but not too many details, so here it is:

I was having a problem in my 2005 focus ZX4. The lights and gages on the instrument cluster/speedometer were acting up: some lights going on when they should not have been, sometimes even when the car was turned off. I read that this is a common problem in the focuses, corrosion forming on the board and shorting out the circuits. This is what I did after reading this on a blog, it was pretty simple.

I removed the dash panel under the steering wheel in order to access the bolts for the dash panel that covers the instrument cluster, then removed that dash panel too. I removed the bolts that held the cluster in place, unplugged the harness in the back of the cluster and removed the unit. I then took the back panel off of the cluster to expose the circuit board. There was noticeable white corrosion/sediment stuff on the board. I sprayed the board with electrical contact spray from any auto store, lightly rubbed it clean with a paper towel and let it dry overnight. Put it all back together and havent had a problem since.

thanks... just wondering if while you had it apart did you notice any small light bulbs inside that are replaceable? I have half of my speedo gauge and my gas gauge not lighting up... will probably take it apart sometime this week if I can spare the time, just wanted to know what I will be getting into beforehand.
thanks.

My 2001 focus 1600 had a problem with the speedometer suddenly going to zero. I read about the circuit board problems and went over all the solder joints on the back with a soldering iron, just keeping it on each joint until it melted. It sounds labourious but didn't take that long to do. You have to be very careful doing it but as it was a last resort before replacing the unit, I thought it was worth it. I had previously tried spraying with WD 40, but with no effect. After the resoldering there was an immediate improvement. Before, the speedo would go off many times during a journey, with the millage LCDs also going to dashes and the engine management light coming on. After the repair, the speedo would just go off once or twice breifly at the start of a journey but then would be fine. I then redid the earth points which are near the washer bottle and are prone to corrosion. This stopped the speedo problem all together and it now works all the time. The earth terminals were very rusty and I would recommend plenty of WD40 before attempting to undo the bolts, to prevent them shearing off.

Welcome.
I would be very surprised if your cluster repair proves to be a long term fix for the speedo zeroing problem. The Focus suffers from two faults in this area. One, as you have found, is poor solder joints on the instrument cluster, and the second is an internal fault in the VSS (Vehicle speed sensor). This item is in the top of the transmission housing and supplies the ECU with data relating to vehicle speed and displays this on the speedo and also has an input to fuelling. Once replaced with a new updated item, it is unlikely you will suffer this problem again. A difficult item to change, and costs around £40, but certainly worth doing.

Thanks for that info. As the fault is no longer there, the solder must have been the problem, and I understand from elsewhere that this fault is known and Ford will replace the whole unit at a reduced charge. I haven't heard that they will also replace the VSS. I wouldn't want to discourage owners to try my fix just because something else might go wrong in the future, and it is something you can do with no expense.I doubt if a main dealer would resort to a soldering iron.
Ido appreciate the info though. I love the idea of a knowledgebase like this. When I was young we just had to resort to a Haynes manual with a picture of some bloke holding a spanner, as if this was any help.

Ford likely uses what's called a "cold" solder with the robots. I seriously doubt that even China uses manual solderers these days. Cold solder is not cold, but momentary electrical arc liquifies the solder as it is applied. It cools nearly instantly. Quick joint, but not a reliable joint. I have yet to remove my 05's instrument cluster, but I'm curious to see if Ford still uses the old printed circuit boards with the really wide circuitry like on their older vehicles. Those are top notch IMO as compared to GM's crapola.

I am afraid I'm going to have to take issue with your comments whynotthinkwhynot. Having worked in the electronics industry for the past 30+ years, mostly in circuit board design- there is not a commercial process that I am aware of, called 'cold soldering'. Most commercial components are soldered by 'wave soldering', where the placed board is passed through a vat of molten solder, making the joints. Surface mount components can also be done this way, but they are generally 'reflowed', where solder paste is applied to the board- the component placed- then infra red heat is used to melt the solder. The vast majority of problems with circuitry these days comes from the use of lead-free solders where the high levels of tin in the solder have led to poor solder joints and the formation of 'tin whiskers' which cause short circuits.

OK
Electronic Technician since 1969.
Be sure to use a GROUNDED soldering iron! Otherwise the stray AC leakage might do in the sensitive circuits.
Also because of Europe's phasing out of using any lead in any products[Rohs], the solder is probably tin. Tin solder has a nasty habit of growing whiskers that will short out adjacent pads etc.
We in the USA still can use leaded solder without any legal hassles unless it goes to Europe.
That junk that you saw on the board... sounds as if the flux was not removed entirely.
Be aware that in the winter time in the North the air is extremely dry and static electricity will occur and can damage sensitive electronics either immediately OR[!] later on.
The amount of static that can destroy electronics can be below human perception. So just because one is not going snap crackle pop on carpet does not mean that one is OK.
I should mention... use of lead solder on plumbing is cause for a great sanction from the government.

Posted via FF Mobile "wave" soldering works OK, unless you have a joint that got contaminated somehow, so no solder sticks.. Had a Marine radio that acted up, on opening it found one joint with no solder, mechanical contact was all that let it work at all... freshly soldered & fixed permanently... Vibration is hell on solder joints in cars, more than one component I`ve fixed just needed resoldering... Unfortunately getting to the board is less & lesss possible on many parts...

I am just curious if the LCD in the instrument cluster can be replaced w/o having to buy a whole instrument cluster? So far the odometer is reading fine, but the trip reset reads of the numbers as though the crystals are getting bad in the LCD?

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